Stimulation of Ca 2+ -dependent neurotransmitter release and presynaptic nerve terminal protein phosphorylation by calmodulin and a calmodulin-like protein isolated from synaptic vesicles

Open Access
Publisher Website
Google Scholar
Abstract
Synaptic vesicles have a Ca2+-dependent protein kinase system that may play a role in mediating Ca2+-stimulated neurotransmitter release and vesicle function. The ability of Ca2+ to initiate norepinephrine release and protein phosphorylation in synaptic vesicle preparations was stimulated by the presence of an endogenous heat-stable vesicle protein fraction. The heat stability and characteristics of this endogenous vesicle fraction were similar to those of calmodulin (Ca2+-dependent regular protein) isolated from rat and bovine brain. Calmodulin, like endogenous heat-stable vesicle factor, restored the ability to stimulate vesicle neurotransmitter release and protein kinase activity. Calmodulin-like vesicle protein and purified calmodulin were equally effective in stimulating cyclic nucleotide-dependent phosphodiesterase, further indicating that these 2 proteins are functionally equivalent. Depolarization-dependent Ca2+ uptake in intact synaptosomes simultaneously stimulated release of neurotransmitter and phosphorylationof particular synaptic vesicle proteins that were shown in the isolated vesicle preparation to be dependent on Ca2+ and calmodulin. The effects of Ca on neurotransmitter release and presynaptic nerve terminal protein phosphorylation may be mediated by endogenous calmodulin-like proteins.

This publication has 21 references indexed in Scilit: